Great question. I stumbled across @cascat07 asking the exact same thing two and a half years ago. 
Nope. Only humans/Abhumans can sense telos.
This is not in fact the case. Unlike Ghaesh, who is a figure of pure legend, Sarcifer was chosen/trained as an Ennearch under the current Thaumatarch. He’s old, but not that old.
Good call. That scene may not appear until Game 3, though.
I haven’t yet firmed up the actual Hegemonic calendar – what year it started counting the Hera Era from, and what they actually call it. Let me chew on that and get back to you.